1. Field of the Invention
The present invention relates to a transmission line formed in a dielectric substrate, an integrated circuit having the dielectric substrate, and a transceiver such as a radar device or a communication device including the integrated circuit.
2. Description of the Related Art
Examples of waveguide-type transmission lines which are integrated with dielectric substrates are disclosed in (1) Japanese Unexamined Patent Application Publication No. 6-53711 and (2) Japanese Unexamined Patent Application Publication No. 10-75108.
According to (1), a dielectric substrate has two or more conductor layers and a plurality of conductive through-holes which are aligned in two lines and which connect the conductor layers. The portion between the two conductor layers and between the two lines of through-holes functions as a waveguide (dielectric-filled waveguide). In a dielectric waveguide line and a wiring substrate according to (2), in addition to the construction of (1), sub-conductor layers are formed between two main conductor layers and on both external sides of via-holes such that the sub-conductor layers are electrically connected to the via-holes.
A surface-electrode circuit is formed on the conductor layers of the dielectric substrate and on a dielectric film formed on the conductor layers, so that the surface-electrode circuit is coupled to the transmission line at a plurality of points. By mounting electronic components on the surface-electrode circuit, an integrated circuit is configured in which the dielectric waveguide line functions as a transmission path of input/output units.
However, in both (1) and (2), the only current path functioning as a wall along the direction perpendicular to the waveguide (and perpendicular to the main surface of the dielectric substrate) is formed by the through-holes or the via-holes. Accordingly, current concentrates at the through-holes or the via-holes and thus conductor loss disadvantageously increases. Further, current flows only in the direction perpendicular to the main surface of the dielectric substrate, not in an oblique direction, due to the through-holes or the via-holes formed in the direction perpendicular to the main surface of the dielectric substrate. In this case, suitable transmission characteristics cannot be obtained, as compared to a common waveguide or dielectric-filled waveguide.
Also, since a signal is directly transmitted from a portion of the dielectric waveguide functioning as an input unit to a portion of the dielectric waveguide functioning as an output unit, the surface-electrode circuit cannot receive the necessary signal. Accordingly, circuit elements mounted on the surface-electrode circuit cannot obtain the required output characteristics.
Further, the signal which is directly transmitted from the input unit to the output unit interferes with an output signal from the surface-electrode circuit, and thus transmission characteristics suitable for an integrated circuit cannot be obtained.
Accordingly, it is an object of the present invention to provide a waveguide-type transmission line having improved transmission characteristics, the transmission line being formed in a dielectric substrate whose main surface is provided with an electrode circuit for mounting electronic components so as to be integrated, and to provide an integrated circuit and a transmitter-receiver including the transmission line.
In order to achieve the above-described object, a dielectric-waveguide-type transmission line according to the present invention comprises: a dielectric substrate; protrusions provided in line, one after another, on at least one main surface of the dielectric substrate; electrodes formed on both main surfaces of the dielectric substrate and on the outer surfaces of the protrusions; a plurality of through-holes for connecting the electrodes, the plurality of through holes being aligned along both sides of the protrusions; an interrupting unit for dividing the transmission line into transmission line segments to interrupt a transmission signal; and a circuit for coupling the transmission line segments separated by the interrupting unit, the circuit being provided on the other main surface of the dielectric substrate. With this arrangement, a signal carried by the transmission line is also directed through the circuit provided on the main surface of the dielectric substrate, and the signal can be prevented from leaking between the protrusions.
Also, the interrupting unit may comprise a protrusion having a predetermined length and a height which is less than the height of the protrusions. Accordingly, the TE10 mode does not transmit between the transmission line segments.
Also, the interrupting unit may comprise a protrusion having a predetermined length and a width which is narrower than the width of the protrusions. Accordingly, the TE01 mode does not transmit between the transmission line segments.
The transmission line may further comprise other through-holes for connecting the electrodes, the other through-holes being provided in an area for interrupting the transmission signal. With this arrangement, the transmission of the signal between the transmission line segments can be effectively suppressed.
Also, one of the protrusions at one transmission line segment may have a different height from the other protrusion at the other transmission line segment. Accordingly, leakage of the signal transmitted from the input-side of the transmission path to the output-side of the transmission path can be suppressed even when the frequency of the signal input to the electrode circuit formed on the main surface of the dielectric substrate is different from the frequency of the signal output from the electrode circuit.
Further, an integrated circuit according to the present invention comprises the above-described transmission line, electronic components mounted on the other main surface of the dielectric substrate, and a circuit for connecting the electronic components. With this arrangement, an integrated circuit having excellent input/output characteristics and transmission characteristics can be obtained.
Further, a transmitter-receiver according to the present invention comprises one of the above-described transmission line and the integrated circuit. Accordingly, a transmitter-receiver having excellent transmission characteristics can be provided.
Other features and advantages of the present invention will become apparent from the following description of embodiments of the invention which refers to the accompanying drawings.